Psychological effect in tunnel group: A driving comfort study based on longitudinal spacing and brightness from...

This study investigates the mechanisms of driver psychological load changes in expressway tunnel groups. By analyzing the heart rate increase rate of participant drivers under different brightness differences and longitudinal spacing conditions, it explores variations in driving comfort and aims to enhance driving safety.

A real-vehicle test was conducted in 5 expressway tunnel groups to collect brightness values and real-time heart rate data from 27 drivers. The relationship between longitudinal spacing, brightness differences, and heart rate increase rate was analyzed. The concept of psychological effect in tunnel groups was proposed to characterize the transmission effect of longitudinal spacing on driving load. The K-means clustering algorithm, combined with heart rate increase rate, was used to classify driving comfort, and a driving comfort model was established considering the coupled effects of brightness differences and longitudinal spacing.

When longitudinal spacing falls within a certain range, it can alleviate psychological load. In the longitudinal spacing section, the heart rate increase rate initially rises and then falls. Exceeding a certain threshold leads to minimal changes in heart rate increase rate. When longitudinal spacing is less than 103 m, the heart rate increase rate reaches a maximum of 26.4%, and the psychological effect is significant. When it exceeds 170 m, the change in driving load becomes negligible, and the psychological effect disappears. Increasing brightness difference expands the range of longitudinal spacing where the psychological effect occurs.

This study identifies the critical ranges of environmental brightness difference and longitudinal spacing contributing to the psychological effect in tunnel groups. It indicates that when the brightness difference is between 500 cd·m^-2 and 2100 cd·m^-2, the psychological effect does not occur. By translating subjective driving comfort into objective parameters, this study facilitates the design of more comfortable tunnel environments, thereby improving traffic safety.